Displays have a clear window to allow light transmission from a light source for customer identification of activity. For example, the light source can be a light pipe, which is a clear plastic part that conveys light indirectly from one source location to another, or directly from a light emitting diode (LED) source. In the context of electronic equipment, manufacturers commonly use LEDs mounted on circuit boards to transmit light to front panels or faceplates through display windows that are viewable by users of the electronic equipment. Accordingly, the manufacturers can enable the users to obtain useful visual information directly from the LEDs of the circuit boards even if the LEDs are nestled deeply behind the front panels or faceplates.
The problem is that the LED can be mounted a considerable distance from the back of the display window, such that at certain viewing angles from the front of the display window, the LED becomes less visible or appears to have shadows. For instance, when the end user is looking at the display window from the side (i.e., not dead on) within blind spots of the light or about 45 degrees relative to the planar surface, the visual information about the system will not be apparent to the end user. Shadowing at the display window can reduce the effective area of the display window and make alphanumeric elements or logos or designs less appreciable. It has been conventional to overcome the shadowing aspects by shortening the distance between the LED and display window, which reduces the viewing angle. In addition, it has been conventional to use a light source larger than the display window, which is a more expensive component to procure and operate and takes additional space within the electronic component. Furthermore, light pipe configurations are problematic because a light pipe is easily mounted out of alignment. In addition, the light pipe provides an unbalanced intensity throughout the light pipe because of the poor internal reflection of the light pipe along the light pipe path. Furthermore, the light pipe is mounted extremely close to the display window (e.g., about 0.020 inches), and is typically sized much larger than the display window to avoid shadowing.
Thus, there remains a need for a system having a display window backlighted with a light source, which has a wider viewing angle so the end user can obtain useful visual information about the system from the light source from the sides of the front panel or faceplate. It would be desirable to provide a display window with a more evenly distributed light across the window and/or with reduced shadowing.